Despite the fact that ideology and party overshadow campaign contributions as determinants of congressional voting behavior, the thesis of this study is that the American Medical Association's contributions have an important policy impact. Their donations had a significant effect on an index of three votes in 1979 in the House of Representatives. The contributions of the AMA had more of an effect than did those of the AFL-CIO. The AMA's money was related to decision-making in the Ways and Means and Energy and Commerce Committees. While the medical lobby does not dominate health care policy, its power should not be underestimated.